This invention relates to ophthalmological surgery techniques which employ an ultraviolet laser used to provide ablative photodecomposition of the surface of the cornea in order to correct vision defects.
Ultraviolet laser based systems and methods are known for enabling ophthalmological surgery on the external surface of the cornea in order to correct vision defects by the technique known as ablative photodecomposition of the cornea. In such systems and methods, the irradiated flux density and exposure time of the cornea to the ultraviolet laser radiation are so controlled as to provide a surface sculpting of the cornea to achieve a desired ultimate surface change in the cornea, all in order to correct an optical defect. Such systems and methods are disclosed in the following U.S. patents and patent applications, the disclosures of which are hereby incorporated by reference: U.S. Pat. No. 4,665,913 issued May 19, 1987 for "Method for Ophthalmological Surgery"; U.S. Pat. No. 4,669,466 issued Jun. 2, 1987 for "Method and Apparatus for Analysis and Correction of Abnormal Refractive Errors of the Eye"; U.S. Pat. No. 4,732,148, issued Mar. 22, 1988 for "Method for Performing Ophthalmic Laser Surgery"; U.S. Pat. No. 4,770,172 issued Sep. 13, 1988 for "Method of Laser-Sculpture of the Optically Used Portion of the Cornea"; U.S. Pat. No. 4,773,414 issued Sep. 27, 1988 for "Method of Laser-Sculpture of the Optically Used Portion of the Cornea; U.S. patent application Ser. No. 109,812 filed Oct. 16, 1987 for "Laser Surgery Method and Apparatus"; and U.S. patent application Ser. No. 081,986 filed Aug. 5, 1987 for "Photorefractive Keratectomy".
The art has now advanced to the stage at which self-contained laser based systems are sold as stand alone units to be installed in a surgeon's operatory or a hospital, as desired. Thus, hospitalization is not necessarily required in order to perform such ophthalmological surgery. Such systems typically include a p.c. (personal computer) type work station, having the usual elements (i.e., keyboard, video display terminal and microprocessor based computer with floppy and hard disk drives and internal memory), and a dedicated microprocessor based computer which interfaces with the p.c. work station and appropriate optical power sensors, motor drivers and control elements of the ultraviolet laser, whose output is delivered through an optical system to the eye of the patient. In use, after the patient has been accommodated on a surgery table or chair, the system is controlled by the operator (either the surgeon or the surgeon and an assistant) in order to prepare the system for the delivery of the radiation to the patient's eye at the appropriate power level and spatial location on the corneal surface. Patient data is typically entered, either manually via the p.c. work station keyboard or from a memory storage element (e.g., a floppy disk), and the system automatically calculates the beam delivery parameters and displays the resulting calculations on the video display terminal, with an optional hard-copy printout via a suitable printer. The laser is also prepared to deliver the appropriate radiation in accordance with the calculated beam delivery parameters, and the delivery system optics are likewise preconditioned. In some systems, a provision is made for permanently recording on a plastic card made of PMMA (polymethylmethacrylate) a spot image of the laser beam used in the surgical operation. This spot is recorded prior to the operation to ensure that the beam power is properly adjusted and to provide a permanent record of the beam used. PMMA is typically used due to the characteristic of this material of having a closely similar ablative photodecomposition response to that of the human corneal tissue. After the surgery has been performed, the resultant data is typically made part of a permanent record, which becomes part of the patient's file.
Such systems and methods are presently emerging as the technique of choice for ophthalmological surgery to correct various vision defects in humans. However, as a relatively recent development this technique in general is still subject to close scrutiny and careful evaluation by the medical community as well as by certain regulatory agencies (e.g., the Food and Drug Administration in the United States of America). Although the p.c. work station provides some ability to collect pertinent information for the evaluation of system performance and to aid in tracking the efficacy of the surgical technique, as well as to provide quality control assistance to the manufacturer of the system, existing laser systems lack a simple effective control mechanism for this purpose.